Although anti-arrhythmic medications and cardiac pacemakers are used most frequently in the elderly, relatively little attention has been focused on characterizing the patterns of the heart beat in normal elderly subjects over an extended period. In the current project, 100 healthy men and women form the Baltimore Longitudinal Study (BLS) over the age of 60 will undergo ambulatory electrocardiography for a 24-hour period, during part of their regular 2 1/2 day visit to the Gerontology Research Center. A small 2 channel Holter recorder will be employed.